Source file src/runtime/cgocall.go
1 // Copyright 2009 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 // Cgo call and callback support. 6 // 7 // To call into the C function f from Go, the cgo-generated code calls 8 // runtime.cgocall(_cgo_Cfunc_f, frame), where _cgo_Cfunc_f is a 9 // gcc-compiled function written by cgo. 10 // 11 // runtime.cgocall (below) calls entersyscall so as not to block 12 // other goroutines or the garbage collector, and then calls 13 // runtime.asmcgocall(_cgo_Cfunc_f, frame). 14 // 15 // runtime.asmcgocall (in asm_$GOARCH.s) switches to the m->g0 stack 16 // (assumed to be an operating system-allocated stack, so safe to run 17 // gcc-compiled code on) and calls _cgo_Cfunc_f(frame). 18 // 19 // _cgo_Cfunc_f invokes the actual C function f with arguments 20 // taken from the frame structure, records the results in the frame, 21 // and returns to runtime.asmcgocall. 22 // 23 // After it regains control, runtime.asmcgocall switches back to the 24 // original g (m->curg)'s stack and returns to runtime.cgocall. 25 // 26 // After it regains control, runtime.cgocall calls exitsyscall, which blocks 27 // until this m can run Go code without violating the $GOMAXPROCS limit, 28 // and then unlocks g from m. 29 // 30 // The above description skipped over the possibility of the gcc-compiled 31 // function f calling back into Go. If that happens, we continue down 32 // the rabbit hole during the execution of f. 33 // 34 // To make it possible for gcc-compiled C code to call a Go function p.GoF, 35 // cgo writes a gcc-compiled function named GoF (not p.GoF, since gcc doesn't 36 // know about packages). The gcc-compiled C function f calls GoF. 37 // 38 // GoF initializes "frame", a structure containing all of its 39 // arguments and slots for p.GoF's results. It calls 40 // crosscall2(_cgoexp_GoF, frame, framesize, ctxt) using the gcc ABI. 41 // 42 // crosscall2 (in cgo/asm_$GOARCH.s) is a four-argument adapter from 43 // the gcc function call ABI to the gc function call ABI. At this 44 // point we're in the Go runtime, but we're still running on m.g0's 45 // stack and outside the $GOMAXPROCS limit. crosscall2 calls 46 // runtime.cgocallback(_cgoexp_GoF, frame, ctxt) using the gc ABI. 47 // (crosscall2's framesize argument is no longer used, but there's one 48 // case where SWIG calls crosscall2 directly and expects to pass this 49 // argument. See _cgo_panic.) 50 // 51 // runtime.cgocallback (in asm_$GOARCH.s) switches from m.g0's stack 52 // to the original g (m.curg)'s stack, on which it calls 53 // runtime.cgocallbackg(_cgoexp_GoF, frame, ctxt). As part of the 54 // stack switch, runtime.cgocallback saves the current SP as 55 // m.g0.sched.sp, so that any use of m.g0's stack during the execution 56 // of the callback will be done below the existing stack frames. 57 // Before overwriting m.g0.sched.sp, it pushes the old value on the 58 // m.g0 stack, so that it can be restored later. 59 // 60 // runtime.cgocallbackg (below) is now running on a real goroutine 61 // stack (not an m.g0 stack). First it calls runtime.exitsyscall, which will 62 // block until the $GOMAXPROCS limit allows running this goroutine. 63 // Once exitsyscall has returned, it is safe to do things like call the memory 64 // allocator or invoke the Go callback function. runtime.cgocallbackg 65 // first defers a function to unwind m.g0.sched.sp, so that if p.GoF 66 // panics, m.g0.sched.sp will be restored to its old value: the m.g0 stack 67 // and the m.curg stack will be unwound in lock step. 68 // Then it calls _cgoexp_GoF(frame). 69 // 70 // _cgoexp_GoF, which was generated by cmd/cgo, unpacks the arguments 71 // from frame, calls p.GoF, writes the results back to frame, and 72 // returns. Now we start unwinding this whole process. 73 // 74 // runtime.cgocallbackg pops but does not execute the deferred 75 // function to unwind m.g0.sched.sp, calls runtime.entersyscall, and 76 // returns to runtime.cgocallback. 77 // 78 // After it regains control, runtime.cgocallback switches back to 79 // m.g0's stack (the pointer is still in m.g0.sched.sp), restores the old 80 // m.g0.sched.sp value from the stack, and returns to crosscall2. 81 // 82 // crosscall2 restores the callee-save registers for gcc and returns 83 // to GoF, which unpacks any result values and returns to f. 84 85 package runtime 86 87 import ( 88 "internal/goarch" 89 "internal/goexperiment" 90 "runtime/internal/sys" 91 "unsafe" 92 ) 93 94 // Addresses collected in a cgo backtrace when crashing. 95 // Length must match arg.Max in x_cgo_callers in runtime/cgo/gcc_traceback.c. 96 type cgoCallers [32]uintptr 97 98 // argset matches runtime/cgo/linux_syscall.c:argset_t 99 type argset struct { 100 args unsafe.Pointer 101 retval uintptr 102 } 103 104 // wrapper for syscall package to call cgocall for libc (cgo) calls. 105 // 106 //go:linkname syscall_cgocaller syscall.cgocaller 107 //go:nosplit 108 //go:uintptrescapes 109 func syscall_cgocaller(fn unsafe.Pointer, args ...uintptr) uintptr { 110 as := argset{args: unsafe.Pointer(&args[0])} 111 cgocall(fn, unsafe.Pointer(&as)) 112 return as.retval 113 } 114 115 var ncgocall uint64 // number of cgo calls in total for dead m 116 117 // Call from Go to C. 118 // 119 // This must be nosplit because it's used for syscalls on some 120 // platforms. Syscalls may have untyped arguments on the stack, so 121 // it's not safe to grow or scan the stack. 122 // 123 //go:nosplit 124 func cgocall(fn, arg unsafe.Pointer) int32 { 125 if !iscgo && GOOS != "solaris" && GOOS != "illumos" && GOOS != "windows" { 126 throw("cgocall unavailable") 127 } 128 129 if fn == nil { 130 throw("cgocall nil") 131 } 132 133 if raceenabled { 134 racereleasemerge(unsafe.Pointer(&racecgosync)) 135 } 136 137 mp := getg().m 138 mp.ncgocall++ 139 140 // Reset traceback. 141 mp.cgoCallers[0] = 0 142 143 // Announce we are entering a system call 144 // so that the scheduler knows to create another 145 // M to run goroutines while we are in the 146 // foreign code. 147 // 148 // The call to asmcgocall is guaranteed not to 149 // grow the stack and does not allocate memory, 150 // so it is safe to call while "in a system call", outside 151 // the $GOMAXPROCS accounting. 152 // 153 // fn may call back into Go code, in which case we'll exit the 154 // "system call", run the Go code (which may grow the stack), 155 // and then re-enter the "system call" reusing the PC and SP 156 // saved by entersyscall here. 157 entersyscall() 158 159 // Tell asynchronous preemption that we're entering external 160 // code. We do this after entersyscall because this may block 161 // and cause an async preemption to fail, but at this point a 162 // sync preemption will succeed (though this is not a matter 163 // of correctness). 164 osPreemptExtEnter(mp) 165 166 mp.incgo = true 167 // We use ncgo as a check during execution tracing for whether there is 168 // any C on the call stack, which there will be after this point. If 169 // there isn't, we can use frame pointer unwinding to collect call 170 // stacks efficiently. This will be the case for the first Go-to-C call 171 // on a stack, so it's preferable to update it here, after we emit a 172 // trace event in entersyscall above. 173 mp.ncgo++ 174 175 errno := asmcgocall(fn, arg) 176 177 // Update accounting before exitsyscall because exitsyscall may 178 // reschedule us on to a different M. 179 mp.incgo = false 180 mp.ncgo-- 181 182 osPreemptExtExit(mp) 183 184 exitsyscall() 185 186 // Note that raceacquire must be called only after exitsyscall has 187 // wired this M to a P. 188 if raceenabled { 189 raceacquire(unsafe.Pointer(&racecgosync)) 190 } 191 192 // From the garbage collector's perspective, time can move 193 // backwards in the sequence above. If there's a callback into 194 // Go code, GC will see this function at the call to 195 // asmcgocall. When the Go call later returns to C, the 196 // syscall PC/SP is rolled back and the GC sees this function 197 // back at the call to entersyscall. Normally, fn and arg 198 // would be live at entersyscall and dead at asmcgocall, so if 199 // time moved backwards, GC would see these arguments as dead 200 // and then live. Prevent these undead arguments from crashing 201 // GC by forcing them to stay live across this time warp. 202 KeepAlive(fn) 203 KeepAlive(arg) 204 KeepAlive(mp) 205 206 return errno 207 } 208 209 // Set or reset the system stack bounds for a callback on sp. 210 // 211 // Must be nosplit because it is called by needm prior to fully initializing 212 // the M. 213 // 214 //go:nosplit 215 func callbackUpdateSystemStack(mp *m, sp uintptr, signal bool) { 216 g0 := mp.g0 217 218 inBound := sp > g0.stack.lo && sp <= g0.stack.hi 219 if mp.ncgo > 0 && !inBound { 220 // ncgo > 0 indicates that this M was in Go further up the stack 221 // (it called C and is now receiving a callback). 222 // 223 // !inBound indicates that we were called with SP outside the 224 // expected system stack bounds (C changed the stack out from 225 // under us between the cgocall and cgocallback?). 226 // 227 // It is not safe for the C call to change the stack out from 228 // under us, so throw. 229 230 // Note that this case isn't possible for signal == true, as 231 // that is always passing a new M from needm. 232 233 // Stack is bogus, but reset the bounds anyway so we can print. 234 hi := g0.stack.hi 235 lo := g0.stack.lo 236 g0.stack.hi = sp + 1024 237 g0.stack.lo = sp - 32*1024 238 g0.stackguard0 = g0.stack.lo + stackGuard 239 g0.stackguard1 = g0.stackguard0 240 241 print("M ", mp.id, " procid ", mp.procid, " runtime: cgocallback with sp=", hex(sp), " out of bounds [", hex(lo), ", ", hex(hi), "]") 242 print("\n") 243 exit(2) 244 } 245 246 if !mp.isextra { 247 // We allocated the stack for standard Ms. Don't replace the 248 // stack bounds with estimated ones when we already initialized 249 // with the exact ones. 250 return 251 } 252 253 // This M does not have Go further up the stack. However, it may have 254 // previously called into Go, initializing the stack bounds. Between 255 // that call returning and now the stack may have changed (perhaps the 256 // C thread is running a coroutine library). We need to update the 257 // stack bounds for this case. 258 // 259 // N.B. we need to update the stack bounds even if SP appears to 260 // already be in bounds. Our "bounds" may actually be estimated dummy 261 // bounds (below). The actual stack bounds could have shifted but still 262 // have partial overlap with our dummy bounds. If we failed to update 263 // in that case, we could find ourselves seemingly called near the 264 // bottom of the stack bounds, where we quickly run out of space. 265 266 // Set the stack bounds to match the current stack. If we don't 267 // actually know how big the stack is, like we don't know how big any 268 // scheduling stack is, but we assume there's at least 32 kB. If we 269 // can get a more accurate stack bound from pthread, use that, provided 270 // it actually contains SP.. 271 g0.stack.hi = sp + 1024 272 g0.stack.lo = sp - 32*1024 273 if !signal && _cgo_getstackbound != nil { 274 // Don't adjust if called from the signal handler. 275 // We are on the signal stack, not the pthread stack. 276 // (We could get the stack bounds from sigaltstack, but 277 // we're getting out of the signal handler very soon 278 // anyway. Not worth it.) 279 var bounds [2]uintptr 280 asmcgocall(_cgo_getstackbound, unsafe.Pointer(&bounds)) 281 // getstackbound is an unsupported no-op on Windows. 282 // 283 // Don't use these bounds if they don't contain SP. Perhaps we 284 // were called by something not using the standard thread 285 // stack. 286 if bounds[0] != 0 && sp > bounds[0] && sp <= bounds[1] { 287 g0.stack.lo = bounds[0] 288 g0.stack.hi = bounds[1] 289 } 290 } 291 g0.stackguard0 = g0.stack.lo + stackGuard 292 g0.stackguard1 = g0.stackguard0 293 } 294 295 // Call from C back to Go. fn must point to an ABIInternal Go entry-point. 296 // 297 //go:nosplit 298 func cgocallbackg(fn, frame unsafe.Pointer, ctxt uintptr) { 299 gp := getg() 300 if gp != gp.m.curg { 301 println("runtime: bad g in cgocallback") 302 exit(2) 303 } 304 305 sp := gp.m.g0.sched.sp // system sp saved by cgocallback. 306 callbackUpdateSystemStack(gp.m, sp, false) 307 308 // The call from C is on gp.m's g0 stack, so we must ensure 309 // that we stay on that M. We have to do this before calling 310 // exitsyscall, since it would otherwise be free to move us to 311 // a different M. The call to unlockOSThread is in this function 312 // after cgocallbackg1, or in the case of panicking, in unwindm. 313 lockOSThread() 314 315 checkm := gp.m 316 317 // Save current syscall parameters, so m.syscall can be 318 // used again if callback decide to make syscall. 319 syscall := gp.m.syscall 320 321 // entersyscall saves the caller's SP to allow the GC to trace the Go 322 // stack. However, since we're returning to an earlier stack frame and 323 // need to pair with the entersyscall() call made by cgocall, we must 324 // save syscall* and let reentersyscall restore them. 325 savedsp := unsafe.Pointer(gp.syscallsp) 326 savedpc := gp.syscallpc 327 exitsyscall() // coming out of cgo call 328 gp.m.incgo = false 329 if gp.m.isextra { 330 gp.m.isExtraInC = false 331 } 332 333 osPreemptExtExit(gp.m) 334 335 if gp.nocgocallback { 336 panic("runtime: function marked with #cgo nocallback called back into Go") 337 } 338 339 cgocallbackg1(fn, frame, ctxt) 340 341 // At this point we're about to call unlockOSThread. 342 // The following code must not change to a different m. 343 // This is enforced by checking incgo in the schedule function. 344 gp.m.incgo = true 345 unlockOSThread() 346 347 if gp.m.isextra { 348 gp.m.isExtraInC = true 349 } 350 351 if gp.m != checkm { 352 throw("m changed unexpectedly in cgocallbackg") 353 } 354 355 osPreemptExtEnter(gp.m) 356 357 // going back to cgo call 358 reentersyscall(savedpc, uintptr(savedsp)) 359 360 gp.m.syscall = syscall 361 } 362 363 func cgocallbackg1(fn, frame unsafe.Pointer, ctxt uintptr) { 364 gp := getg() 365 366 if gp.m.needextram || extraMWaiters.Load() > 0 { 367 gp.m.needextram = false 368 systemstack(newextram) 369 } 370 371 if ctxt != 0 { 372 s := append(gp.cgoCtxt, ctxt) 373 374 // Now we need to set gp.cgoCtxt = s, but we could get 375 // a SIGPROF signal while manipulating the slice, and 376 // the SIGPROF handler could pick up gp.cgoCtxt while 377 // tracing up the stack. We need to ensure that the 378 // handler always sees a valid slice, so set the 379 // values in an order such that it always does. 380 p := (*slice)(unsafe.Pointer(&gp.cgoCtxt)) 381 atomicstorep(unsafe.Pointer(&p.array), unsafe.Pointer(&s[0])) 382 p.cap = cap(s) 383 p.len = len(s) 384 385 defer func(gp *g) { 386 // Decrease the length of the slice by one, safely. 387 p := (*slice)(unsafe.Pointer(&gp.cgoCtxt)) 388 p.len-- 389 }(gp) 390 } 391 392 if gp.m.ncgo == 0 { 393 // The C call to Go came from a thread not currently running 394 // any Go. In the case of -buildmode=c-archive or c-shared, 395 // this call may be coming in before package initialization 396 // is complete. Wait until it is. 397 <-main_init_done 398 } 399 400 // Check whether the profiler needs to be turned on or off; this route to 401 // run Go code does not use runtime.execute, so bypasses the check there. 402 hz := sched.profilehz 403 if gp.m.profilehz != hz { 404 setThreadCPUProfiler(hz) 405 } 406 407 // Add entry to defer stack in case of panic. 408 restore := true 409 defer unwindm(&restore) 410 411 if raceenabled { 412 raceacquire(unsafe.Pointer(&racecgosync)) 413 } 414 415 // Invoke callback. This function is generated by cmd/cgo and 416 // will unpack the argument frame and call the Go function. 417 var cb func(frame unsafe.Pointer) 418 cbFV := funcval{uintptr(fn)} 419 *(*unsafe.Pointer)(unsafe.Pointer(&cb)) = noescape(unsafe.Pointer(&cbFV)) 420 cb(frame) 421 422 if raceenabled { 423 racereleasemerge(unsafe.Pointer(&racecgosync)) 424 } 425 426 // Do not unwind m->g0->sched.sp. 427 // Our caller, cgocallback, will do that. 428 restore = false 429 } 430 431 func unwindm(restore *bool) { 432 if *restore { 433 // Restore sp saved by cgocallback during 434 // unwind of g's stack (see comment at top of file). 435 mp := acquirem() 436 sched := &mp.g0.sched 437 sched.sp = *(*uintptr)(unsafe.Pointer(sched.sp + alignUp(sys.MinFrameSize, sys.StackAlign))) 438 439 // Do the accounting that cgocall will not have a chance to do 440 // during an unwind. 441 // 442 // In the case where a Go call originates from C, ncgo is 0 443 // and there is no matching cgocall to end. 444 if mp.ncgo > 0 { 445 mp.incgo = false 446 mp.ncgo-- 447 osPreemptExtExit(mp) 448 } 449 450 // Undo the call to lockOSThread in cgocallbackg, only on the 451 // panicking path. In normal return case cgocallbackg will call 452 // unlockOSThread, ensuring no preemption point after the unlock. 453 // Here we don't need to worry about preemption, because we're 454 // panicking out of the callback and unwinding the g0 stack, 455 // instead of reentering cgo (which requires the same thread). 456 unlockOSThread() 457 458 releasem(mp) 459 } 460 } 461 462 // called from assembly. 463 func badcgocallback() { 464 throw("misaligned stack in cgocallback") 465 } 466 467 // called from (incomplete) assembly. 468 func cgounimpl() { 469 throw("cgo not implemented") 470 } 471 472 var racecgosync uint64 // represents possible synchronization in C code 473 474 // Pointer checking for cgo code. 475 476 // We want to detect all cases where a program that does not use 477 // unsafe makes a cgo call passing a Go pointer to memory that 478 // contains an unpinned Go pointer. Here a Go pointer is defined as a 479 // pointer to memory allocated by the Go runtime. Programs that use 480 // unsafe can evade this restriction easily, so we don't try to catch 481 // them. The cgo program will rewrite all possibly bad pointer 482 // arguments to call cgoCheckPointer, where we can catch cases of a Go 483 // pointer pointing to an unpinned Go pointer. 484 485 // Complicating matters, taking the address of a slice or array 486 // element permits the C program to access all elements of the slice 487 // or array. In that case we will see a pointer to a single element, 488 // but we need to check the entire data structure. 489 490 // The cgoCheckPointer call takes additional arguments indicating that 491 // it was called on an address expression. An additional argument of 492 // true means that it only needs to check a single element. An 493 // additional argument of a slice or array means that it needs to 494 // check the entire slice/array, but nothing else. Otherwise, the 495 // pointer could be anything, and we check the entire heap object, 496 // which is conservative but safe. 497 498 // When and if we implement a moving garbage collector, 499 // cgoCheckPointer will pin the pointer for the duration of the cgo 500 // call. (This is necessary but not sufficient; the cgo program will 501 // also have to change to pin Go pointers that cannot point to Go 502 // pointers.) 503 504 // cgoCheckPointer checks if the argument contains a Go pointer that 505 // points to an unpinned Go pointer, and panics if it does. 506 func cgoCheckPointer(ptr any, arg any) { 507 if !goexperiment.CgoCheck2 && debug.cgocheck == 0 { 508 return 509 } 510 511 ep := efaceOf(&ptr) 512 t := ep._type 513 514 top := true 515 if arg != nil && (t.Kind_&kindMask == kindPtr || t.Kind_&kindMask == kindUnsafePointer) { 516 p := ep.data 517 if t.Kind_&kindDirectIface == 0 { 518 p = *(*unsafe.Pointer)(p) 519 } 520 if p == nil || !cgoIsGoPointer(p) { 521 return 522 } 523 aep := efaceOf(&arg) 524 switch aep._type.Kind_ & kindMask { 525 case kindBool: 526 if t.Kind_&kindMask == kindUnsafePointer { 527 // We don't know the type of the element. 528 break 529 } 530 pt := (*ptrtype)(unsafe.Pointer(t)) 531 cgoCheckArg(pt.Elem, p, true, false, cgoCheckPointerFail) 532 return 533 case kindSlice: 534 // Check the slice rather than the pointer. 535 ep = aep 536 t = ep._type 537 case kindArray: 538 // Check the array rather than the pointer. 539 // Pass top as false since we have a pointer 540 // to the array. 541 ep = aep 542 t = ep._type 543 top = false 544 default: 545 throw("can't happen") 546 } 547 } 548 549 cgoCheckArg(t, ep.data, t.Kind_&kindDirectIface == 0, top, cgoCheckPointerFail) 550 } 551 552 const cgoCheckPointerFail = "cgo argument has Go pointer to unpinned Go pointer" 553 const cgoResultFail = "cgo result is unpinned Go pointer or points to unpinned Go pointer" 554 555 // cgoCheckArg is the real work of cgoCheckPointer. The argument p 556 // is either a pointer to the value (of type t), or the value itself, 557 // depending on indir. The top parameter is whether we are at the top 558 // level, where Go pointers are allowed. Go pointers to pinned objects are 559 // allowed as long as they don't reference other unpinned pointers. 560 func cgoCheckArg(t *_type, p unsafe.Pointer, indir, top bool, msg string) { 561 if t.PtrBytes == 0 || p == nil { 562 // If the type has no pointers there is nothing to do. 563 return 564 } 565 566 switch t.Kind_ & kindMask { 567 default: 568 throw("can't happen") 569 case kindArray: 570 at := (*arraytype)(unsafe.Pointer(t)) 571 if !indir { 572 if at.Len != 1 { 573 throw("can't happen") 574 } 575 cgoCheckArg(at.Elem, p, at.Elem.Kind_&kindDirectIface == 0, top, msg) 576 return 577 } 578 for i := uintptr(0); i < at.Len; i++ { 579 cgoCheckArg(at.Elem, p, true, top, msg) 580 p = add(p, at.Elem.Size_) 581 } 582 case kindChan, kindMap: 583 // These types contain internal pointers that will 584 // always be allocated in the Go heap. It's never OK 585 // to pass them to C. 586 panic(errorString(msg)) 587 case kindFunc: 588 if indir { 589 p = *(*unsafe.Pointer)(p) 590 } 591 if !cgoIsGoPointer(p) { 592 return 593 } 594 panic(errorString(msg)) 595 case kindInterface: 596 it := *(**_type)(p) 597 if it == nil { 598 return 599 } 600 // A type known at compile time is OK since it's 601 // constant. A type not known at compile time will be 602 // in the heap and will not be OK. 603 if inheap(uintptr(unsafe.Pointer(it))) { 604 panic(errorString(msg)) 605 } 606 p = *(*unsafe.Pointer)(add(p, goarch.PtrSize)) 607 if !cgoIsGoPointer(p) { 608 return 609 } 610 if !top && !isPinned(p) { 611 panic(errorString(msg)) 612 } 613 cgoCheckArg(it, p, it.Kind_&kindDirectIface == 0, false, msg) 614 case kindSlice: 615 st := (*slicetype)(unsafe.Pointer(t)) 616 s := (*slice)(p) 617 p = s.array 618 if p == nil || !cgoIsGoPointer(p) { 619 return 620 } 621 if !top && !isPinned(p) { 622 panic(errorString(msg)) 623 } 624 if st.Elem.PtrBytes == 0 { 625 return 626 } 627 for i := 0; i < s.cap; i++ { 628 cgoCheckArg(st.Elem, p, true, false, msg) 629 p = add(p, st.Elem.Size_) 630 } 631 case kindString: 632 ss := (*stringStruct)(p) 633 if !cgoIsGoPointer(ss.str) { 634 return 635 } 636 if !top && !isPinned(ss.str) { 637 panic(errorString(msg)) 638 } 639 case kindStruct: 640 st := (*structtype)(unsafe.Pointer(t)) 641 if !indir { 642 if len(st.Fields) != 1 { 643 throw("can't happen") 644 } 645 cgoCheckArg(st.Fields[0].Typ, p, st.Fields[0].Typ.Kind_&kindDirectIface == 0, top, msg) 646 return 647 } 648 for _, f := range st.Fields { 649 if f.Typ.PtrBytes == 0 { 650 continue 651 } 652 cgoCheckArg(f.Typ, add(p, f.Offset), true, top, msg) 653 } 654 case kindPtr, kindUnsafePointer: 655 if indir { 656 p = *(*unsafe.Pointer)(p) 657 if p == nil { 658 return 659 } 660 } 661 662 if !cgoIsGoPointer(p) { 663 return 664 } 665 if !top && !isPinned(p) { 666 panic(errorString(msg)) 667 } 668 669 cgoCheckUnknownPointer(p, msg) 670 } 671 } 672 673 // cgoCheckUnknownPointer is called for an arbitrary pointer into Go 674 // memory. It checks whether that Go memory contains any other 675 // pointer into unpinned Go memory. If it does, we panic. 676 // The return values are unused but useful to see in panic tracebacks. 677 func cgoCheckUnknownPointer(p unsafe.Pointer, msg string) (base, i uintptr) { 678 if inheap(uintptr(p)) { 679 b, span, _ := findObject(uintptr(p), 0, 0) 680 base = b 681 if base == 0 { 682 return 683 } 684 if goexperiment.AllocHeaders { 685 tp := span.typePointersOfUnchecked(base) 686 for { 687 var addr uintptr 688 if tp, addr = tp.next(base + span.elemsize); addr == 0 { 689 break 690 } 691 pp := *(*unsafe.Pointer)(unsafe.Pointer(addr)) 692 if cgoIsGoPointer(pp) && !isPinned(pp) { 693 panic(errorString(msg)) 694 } 695 } 696 } else { 697 n := span.elemsize 698 hbits := heapBitsForAddr(base, n) 699 for { 700 var addr uintptr 701 if hbits, addr = hbits.next(); addr == 0 { 702 break 703 } 704 pp := *(*unsafe.Pointer)(unsafe.Pointer(addr)) 705 if cgoIsGoPointer(pp) && !isPinned(pp) { 706 panic(errorString(msg)) 707 } 708 } 709 } 710 return 711 } 712 713 for _, datap := range activeModules() { 714 if cgoInRange(p, datap.data, datap.edata) || cgoInRange(p, datap.bss, datap.ebss) { 715 // We have no way to know the size of the object. 716 // We have to assume that it might contain a pointer. 717 panic(errorString(msg)) 718 } 719 // In the text or noptr sections, we know that the 720 // pointer does not point to a Go pointer. 721 } 722 723 return 724 } 725 726 // cgoIsGoPointer reports whether the pointer is a Go pointer--a 727 // pointer to Go memory. We only care about Go memory that might 728 // contain pointers. 729 // 730 //go:nosplit 731 //go:nowritebarrierrec 732 func cgoIsGoPointer(p unsafe.Pointer) bool { 733 if p == nil { 734 return false 735 } 736 737 if inHeapOrStack(uintptr(p)) { 738 return true 739 } 740 741 for _, datap := range activeModules() { 742 if cgoInRange(p, datap.data, datap.edata) || cgoInRange(p, datap.bss, datap.ebss) { 743 return true 744 } 745 } 746 747 return false 748 } 749 750 // cgoInRange reports whether p is between start and end. 751 // 752 //go:nosplit 753 //go:nowritebarrierrec 754 func cgoInRange(p unsafe.Pointer, start, end uintptr) bool { 755 return start <= uintptr(p) && uintptr(p) < end 756 } 757 758 // cgoCheckResult is called to check the result parameter of an 759 // exported Go function. It panics if the result is or contains any 760 // other pointer into unpinned Go memory. 761 func cgoCheckResult(val any) { 762 if !goexperiment.CgoCheck2 && debug.cgocheck == 0 { 763 return 764 } 765 766 ep := efaceOf(&val) 767 t := ep._type 768 cgoCheckArg(t, ep.data, t.Kind_&kindDirectIface == 0, false, cgoResultFail) 769 } 770